Fifth generation (5G) new radio (NR) transmission systems may include grant free uplink transmissions as a feature. In grant free uplink transmission, packets are transmitted without waiting for a grant of resources for the uplink. Grant free uplink transmission may be used for internet of things (IoT) and other scenarios to increase capacity. Grant free uplink may be especially beneficial for intermittent small packets, e.g., occasional reports from a sensor or other device, keep-alive packets from an application, or the like. There may be some services which regularly use grant free transmission, and other services that have a mix of small packets suitable for grant free transmission and larger data blocks that require an uplink grant for acceptable performance.
In some cases, there may be specific services or specific data flows that are unconditionally configured to use grant-free transmission. Accordingly, a grant free mechanism may be used for the channels corresponding to these services or flows, resulting in a class of logical channels assigned specifically to carry grant free transmissions. When certain logical channels are assigned to grant free use, the grant free logical channels have a separate scheduler that uses only the grant free physical layer (PHY) resources, i.e., the portion of physical layer resources in the system that are permitted to be occupied by grant free transmissions. Such PHY resources may be characterized as a subset of the radio resources, defined for example by timing, carrier or subcarrier frequency, code assignment, and so on.